It is well known in the veterinary field to use boluses to deliver medicaments to ruminants. Boluses can be used to treat specific ailments or as a preventative for specific conditions.
A bolus is a delivery device for the long term delivery of medicaments to an animal. Typically, the bolus consists of a housing with one open end, often made of plastic or metal alloy which contains a series of tablets. An example of such a bolus is disclosed in New Zealand Patent No. 220024 to Castex Products Limited.
The bolus is delivered into the stomach of the animal to be treated where the rumen fluids of the stomach act to erode the exposed tablet, thus releasing the medicament into the circulatory system of the animal.
Once all of the tablets have eroded, the housing (if made from metal) decays into its metal components and is usually passed through the animal by excretion. Some bolus housings made of plastic may be regurgitated whilst the animal is ruminating, or is retained by the animal in the rumen. The housing is made from biocompatible materials and thus is not harmful to the animal.
The tablets are designed to erode at relatively specific rates. This is to ensure that the animal does not receive particular medicaments in excess of a specific threshold, which may be harmful to the animal being treated. Exceeding a specific threshold of medicaments may also result in negative side effects for the animal being treated.
Boluses are ideal for the slow release of medicaments over time, thus avoiding the requirement to repeatedly dose the animal. Indeed, the bolus disclosed in New Zealand Patent No. 220024 is intended to remain in the rumen for several months.
As previously discussed, the release rate is designed to ensure that the medicament to be delivered does not exceed a certain threshold. This threshold is usually measured by the amount of medicament in the circulatory system of the animal relative to its body mass.
It will be appreciated therefore that a bolus intended for use with an adult cow may not be suitable for use with a calf, due to the difference in the body mass of these respective animals. The amount of medicament released by the bolus may in excess of what is considered to be a safe threshold for a calf.
Nor is a bolus intended for use with a calf suitable for the use with an adult cow, as the medicament delivered would be insufficient for the condition being treated in the adult cow.
In these instances, often the level of medicament which is intended to kill parasites or bacteria is not at a sufficient level to ensure complete eradiation of all the targeted parasites or bacteria. The remaining parasites or bacteria can build up resistance to the medicament, and thus over time the medicament may become unsuitable for treating the specific condition.
When raising cattle, it is economically beneficial to use methods which encourage rapid growth rates of juvenile cattle. Thus it is not uncommon for a calf to increase its body mass by more than 10% within a month. Because of the significant growth rates, it can be difficult to satisfactorily treat specific condition such as parasitic infestations.
It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.
All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.
It is acknowledged that the term ‘comprise’ may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term ‘comprise’ shall have an inclusive meaning—i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements.
This rationale will also be used when the term ‘comprised’ or ‘comprising’ is used in relation to one or more steps in a method or process.